1. Field of the Invention
The present invention relates to a semiconductor light emitting device including a plurality of light emitting devices, and an optical pickup unit and an information recording/reproduction apparatus provided therewith.
2. Description of the Related Art
In recent years, in the field of laser diodes (LD), a multi-wavelength laser device having a plurality of light emitting device sections with different light emitting wavelengths on the same substrate (or base) has been actively developed. The multi-wavelength laser device is used as, for example, a light source for an optical disk unit.
In such an optical disk unit, laser light in 700 nm band is used for reproduction of a CD (Compact Disk), and is used for recording and reproduction of a recordable optical disk such as a CD-R (CD Recordable), a CD-RW (CD Rewritable), and an MD (Mini Disk). In addition, laser light in 600 nm band is used for recording and reproduction of a DVD (Digital Versatile Disk). By mounting the multi-wavelength laser device on the optical disk unit, recording or reproduction becomes available for a plurality of types of existing optical disks. Further, a short-wavelength laser device (400 nm band) using a nitride Group III-V compound semiconductor typified by GaN, AlGaN mixed crystal, and GaInN mixed crystal has been realized, and they work toward practical use of such a short-wavelength laser device as a light source of a higher density optical disk. By developing a multi-wavelength laser device including the short-wavelength laser device, applications can be more widened.
As a three-wavelength laser device having a GaN light emitting device section described above, in the past, the following device has been suggested (Japanese Patent No. 3486900). In the device, a first light emitting device in 400 nm band (for example, 405 nm) is formed by growing a GaN semiconductor on a substrate made of GaN (gallium nitride). A second light emitting device is formed by providing a device having a light emitting device section in 600 nm band (for example, 650 nm) by growing an AlGaInP semiconductor and a device having a light emitting device section in 700 nm band (for example, 780 nm) by growing an AlGaAs semiconductor on the same substrate made of GaAs (gallium arsenide) in parallel with each other. The first light emitting device and the second light emitting device are layered in this order on a support base (heat sink).